In control systems requiring high reliability, redundant electronic controllers are often connected in parallel for backup in the event of a failure. In these systems, the inputs from the sensors and the outputs from the electronic controllers may be connected to ground in a manner that creates high current ground paths and loops in the circuit, causing flyback currents to flow into the electronic controllers and undesired noise on the input signals. An example of this occurs when the solenoid of an inductive component in an engine control system such as a coil or an engine injector has a common ground with one or more pulse width modulated (PWM) type sensors such as a throttle sensor. In this situation, noise is likely to be coupled with the sensor signal. If a momentary spike in the noise level reaches the threshold detection level for the controller input signal, the controller will respond due to the noise instead of the sensor signal, thereby degrading system performance. The noise may also feed back into the sensor circuit and cause false triggering of the throttle sensor PWM signal. Similar noise problems may be caused when a variety of components produced by different manufacturers are used in the same controller.
It is usually expensive and difficult to eliminate this noise. Shielding the wiring, or a redesign of the wiring harness are two potential solutions to the noise problem, however, both are very expensive to implement. Another potential solution is to develop a software program to filter the signal, but developing and installing the software is also very expensive. Relay switches may be used to connect the solenoid common, but system reliability will be lowered. It is also desired to have a cost effective means to correct the noise problem on newly manufactured electronic controllers as well as to retrofit controllers already in use.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.